I can't work in DXF. After I have downloaded the file, I can't on the lines with my mouse. What is wrong?
Pipe Designer doesn't give you the ability to work with the CAD files. You will need something else for that. This is specified on the developer's page right next to the Pipe Designer information.
Download the A9CAD software to open and work with the DXF files after they've been exported from Pipe Designer.
Download page: http://ypvsbox.free.fr/?page_id=174